Pendant Drop Method Research Articles

THE ROLE OF FIBRINOGEN IN SERUM AND PLASMA BLOOD TENSIO- AND RIOMETRY IN CORONARY HEART DISEASE AND VALVE LESIONS PATIENTS

Background. Insight into blood viscosity in terms of its physical and biochemical properties carries significant clinical value. By understanding the relationship between the physical properties of blood and physiology, a potentially powerful tool for diagnosing early signs of many diseases can be discovered.
 Purpose. To identify the effect of fibrinogen on tensio- and rheometric characteristics of blood plasma and serum in patients with coronary heart disease and with mitral and/or aortic valve disease.
 Materials and methods. Prospective non-randomized study. The study of dynamic, equilibrium surface tension and viscoelastic modulus was performed by the pendant drop method using a PAT-1 device (Sinterface Technologies, Germany). We measured parameters characterizing the surface tension and dilatation rheology of blood serum such as: dynamic surface tension at an adsorption time of 100 s (γ), equilibrium surface tension (γ ∞) (adsorption time 2500 s), viscoelastic modulus |E|, and phase angle (φ) at frequencies of 0.1 and 0.01 Hz.
 All patients under study were divided into 3 groups. The healthy volunteers (30 subjects) without chronic diseases and active complaints aged 49 to 78 years (mean age, 61.1±1.1 years) comprised the comparison group (group 1).
 Group 2 - 40 patients with coronary heart disease (CHD) aged 49 to 77 years (mean age 62.2±1.3 years) who underwent bypass surgery to treat atherosclerotic coronary vessels (2 to 5 bypasses).
 Group 3 - 30 patients with cardiac mitral and/or aortic valve lesions aged 52 to 78 years (mean age 61.3±1.2 years). They underwent mitral and/or aortic valve replacement with mechanical prostheses.
 The most common pathophysiological syndrome in patients due to coronary artery or heart valve lesions was chronic heart failure (CHF) (stage 2A-2B according to Vasilenko-Strazhesko classification).
 Results. Characteristic γ100s of blood serum and plasma had significant difference in both patients’ groups, possibly due to the role of coagulation and anti-coagulation system proteins’ role in dynamic surface tension of plasma in a shorter timeframe (up to 100 s.). The increase in Δγ100s in both patients’ groups by day 7 of the postoperative period indicates an increasing dynamic surface tension of serum compared to plasma. Plasma of perioperative patients does not differ from the comparison group by its surface-equilibrium properties. Accordingly, the Δγ∞s values in groups 1 and 2 both before surgery and on days 1 and 7 of the postoperative period are almost identical, pointing to no difference in the amount of surfactants tending to adsorb on the droplet surface. Alterations of viscoelastic modulus |E| and phase angle (φ) at 0.1 and 0.01 Hz in the perioperative period indicate changes in qualitative and quantitative characteristics of circulating blood with variation in individual homeostasis characteristics, resulting in an increase in surface elasticity combined with an almost unchanged surface viscosity.
 Conclusion. Dynamic and equilibrium surface tension parameters in patients’ plasma differ from those in serum due to the presence of fibrinogen and other proteins of the blood coagulation system.

Method to Measure Surface Tension of Microdroplets Using Standard AFM Cantilever Tips.

Surface tension is a physical property that is central to our understanding of wetting phenomena. One could easily measure liquid surface tension using commercially available tensiometers (e.g., Wilhelmy plate method) or by optical imaging (e.g., pendant drop method). However, such instruments are designed for bulk liquid volumes on the order of milliliters. In order to perform similar measurements on extremely small sample volumes in the range of femtoliters, atomic force microscope (AFM) is considered as a promising tool. It was previously reported that by fabricating a special "nanoneedle"-shaped cantilever probe, a Wilhelmy-like experiment can be performed with AFM. By measuring the capillary force between such special probes and a liquid surface, surface tension could be calculated. Here, we carried out measurements on microscopic droplets with AFM, but instead, using standard pyramidal cantilever tips. The cantilevers were coated with a hydrophilic polyethylene glycol-based polymer brush in a simple one-step process, which reduced its contact angle hysteresis for most liquids. Numerical simulations of a liquid drop interacting with a pyramidal or conical geometry were used to calculate surface tension from the experimentally measured force. The results on micrometer-sized drops agree well with bulk tensiometer measurement of three test liquids (mineral oil, ionic liquid, and glycerol), within a maximum error of 10%. Our method eliminates the need for specially fabricated "nanoneedle" tips, thus reducing the complexity and cost of measurement.

Abnormal wetting behavior of supercooled deep eutectic solvents

The supercooled liquid state of a deep eutectic solvent (DES) composed of a mixture of choline chloride and citric acid monohydrate (CA) is studied for different molar ratios at room temperature. The supercooled DESs are highly stable and exhibit viscosities exceeding 104 mPa∙s, which increase with higher CA content. The dependence of the viscosity on temperature can be described by the Arrhenius equation, where the activation energy increases with CA content. Due to extremely high viscosity, the surface tension measurement using the pendant drop method requires a stepwise pressurization approach, and the relaxation to equilibrium is quite slow. Surface tensions were found to be considerably high, comparable to that of water, and they slightly decrease with higher CA concentration. The wetting behavior of supercooled DESs on glass is characterized by an unusually slow spreading process. The equilibrium contact angle increases with higher CA content. Moreover, wetting competition of a liquid bridge between dissimilar surfaces was also examined, and it is interesting to find the outcome dependent on the contact time, in addition to surface wettability.

Identification of machine learning neural-network techniques for prediction of interfacial tension reduction by zein based colloidal particles

In this work, five different models of the artificial neural networks (ANNs) called feedforward, cascadeforward, timedelay, layrec and narx were used for IFT prediction as a function of biopolymers (zein and water-soluble portion of Zedo gum (WZG)) contents, pH, and time based on the experimental data. The architecture of the ANN models consisted of four inputs, one hidden layer and one output layer by considering the range of 1–60 neurons and the tansig activation function in the hidden layer. The experimental IFT data obtained from pendant drop method and drop shape analyzer (DSA) instrument were used to train the ANN models. The relative root mean square error (rRMSE) for the mentioned models were in the range of 0.68%− 2.51% and the overall score of timedelay model was higher than other models. Moreover, the relative importance index of the input data for more detailed assessment of IFT was determined for time delay model as the best model to predict IFT. Analysis showed that the impacts of time and zein content on IFT were greater than other factors. The results of this research showed the considerable ability of timedelay model (a data-based and knowledge-based combined approach) to predict IFT. This model can be used by food industry engineers as a very useful and cost-effective tool for process optimization and control the stability of emulsions.

High-Temperature Measurements on Viscosity and Surface Tension of the Ionic Liquid 1-Ethyl-3-methylimidazolium Bis(trifluoromethylsulfonyl)imide ([EMIM][NTf2]) up to 473 K

In the present study, the viscosity and surface tension of the commercial low-viscosity ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)-imide ([EMIM][NTf2]) were determined by a combination of surface light scattering (SLS) and the pendant-drop (PD) method between (303 and 473) K. Both methods operating at thermodynamic equilibrium were applied inside the same measurement cell at identical experimental conditions under an argon atmosphere at 0.1 MPa. For SLS measurements performed in the temperature range from (303 to 323) K, the overdamped behavior of the surface fluctuations allowed access to the viscosity with an expanded uncertainty of 2.3 % using the surface tensions determined via the PD method with an uncertainty of 2 % as input quantities. Above 323 K up to 473 K, the oscillatory behavior of the probed surface fluctuations by SLS enabled a simultaneous determination of viscosity and surface tension with average expanded uncertainties of (4 and 3) %, respectively. Multiple repetition measurements by both methods have been conducted at 323 K after experiments at larger temperatures up to 473 K, and the consistency of their results could indicate a sound thermal stability of the IL sample. The mutual agreement of the surface tension results from SLS and the PD method between (353 and 473) K demonstrates that both techniques analyze the very same IL surface. For both properties, the results from this work agree well with the majority of experimental data reported in the literature typically up to 353 K. In summary, the viscosity and surface tension results presented in this study contribute to an improved data landscape for this particular IL and ILs in general at elevated temperatures.

Role of Distance from Equilibrium in the Fragmentation Kinetics of Block Copolymer Micelles

The fragmentation kinetics of 1,2-polybutadiene-b-poly(ethylene oxide) (Mn = 17.2 kDa and fPEO = 0.38) block copolymer micelles have been examined with an emphasis on elucidating the role of driving force for micellar fragmentation, represented by the aggregation number ratio Q/Qeq. Large micelles with size Q > Qeq were formed in an ionic liquid [C2mim][TFSI] by the direct dissolution method. A broad range of Q/Qeq was then obtained by altering the solvent quality after micelle formation by addition of a second solvent, selected from a series of imidazolium-based ionic liquids [Cxmim][TFSI] with x = 2, 4, 6, 8, 10, and 12. In order to quantify the change in solvent quality by dilution, the interfacial tension γ between the different ionic liquids and 1,2-polybutadiene homopolymer was determined using the pendant drop method. Micelles in a solution diluted with a second ionic liquid with x ≥ 2 were equilibrated by high-temperature annealing at 170 °C, during which in situ dynamic light-scattering measurements were made to follow the decay of average micelle size with time. Micelles were further characterized using small-angle X-ray scattering and cryogenic transmission electron microscopy to obtain micelle core size distributions. Qeq and γ were found to exhibit a power-law correlation, Qeq ∼ γ6/5, in accordance with the scaling prediction for star-like micelles. The reduction in γ on dilution with a lower γ solvent (x > 2) results in a smaller equilibrium micelle size, enabling access to a higher Q/Qeq, in the range from 1.1 to 5. The rate of fragmentation was found to increase significantly with an increase in Q/Qeq, thus the greater thermodynamic driving force leads to a systematic acceleration of fragmentation kinetics. The detailed mechanism by which micelles with Q ≫ Qeq achieve Qeq remains to be elucidated; the data suggest that it is not a sequential process but concerted.

Organo-Bentonite-Coated Interfaces: Interfacial Properties and Cyclic Response

The accumulation of amphiphilic molecules, nanoparticles, or microorganisms at interfaces has important implications for multiphase flow in porous media. We optimize the composition of stable organo-bentonite suspensions to enhance particle adsorption onto the oil–water interface. Then, we use the pendant drop method to explore time-dependent effects on surface tension and the consequences of contraction–expansion cycles. Brownian motion brings organo-bentonite particles to the oil–water interface where they adsorb and accumulate to reduce the apparent interfacial tension in time. The adsorption energy of platy organo-bentonite particles is significantly higher than the adsorption energy of spherical nanoparticles of the same volume. Then, a shell-like interface develops after particle jamming during droplet contraction, and further contraction leads to shell buckling and wrinkle formation (rather than desorption). The shell-like interface experiences an anisotropic stress field and cannot be described by the Young–Laplace equation. The evolution of interfacial tension during contraction and expansion shows strong hysteresis; furthermore, the results suggest that the number of adsorbed particles at the interface increases with the number of cycles. Natural clay nanoparticles can facilitate the development of cost-effective and environmentally friendly alternatives for field-scale applications.

Surface tension and viscosity of binary ionic liquid mixtures from high vacuum up to pressures of 10 MPa

In the present study, we investigated the surface tension and viscosity of binary ionic liquid (IL) mixtures at or close to saturation conditions from high vacuum conditions up to elevated pressures. We studied four different mixtures of 1,3-bis(2-(2-methoxyethoxy)ethyl)imida-zolium iodide ([(mPEG2)2Im]I) and 1-methyl-3-octylimidazolium hexafluorophosphate ([C8C1Im][PF6]) with [C8C1Im][PF6] mole contents between (4.6 and 49.8) mol%. Argon (Ar) gas of relatively low solubility was used to vary the applied pressure between (0.1 and 10) MPa. For temperatures from (303 to 363) K, the surface tension obtained by the pendant-drop (PD) method was used to determine the saturated liquid viscosity from surface light scattering (SLS). These studies are complemented by additional PD measurements under ultraclean high vacuum (HV) conditions in a second setup. At about 0.1 MPa, the surface tension and viscosity of the IL mixtures show negative deviations from a linear mixing rule based on the molar bulk composition, which is more pronounced at lower temperatures. The surface tension values at 0.1 MPa and under HV agree with each other and lie closer to the values of [C8C1Im][PF6] that has a distinctly lower surface tension than [(mPEG2)2Im]I and is surface-active. For the equimolar IL mixture at 303 K, an increase in the pressure up to 10 MPa has a negligible influence on the viscosity, while it causes a distinct reduction in the surface tension compared to the value at 0.1 MPa. The pressure-dependent relative change for the viscosity of the ternary mixtures of the two ILs and Ar corresponds well to the mean values of the positive and negative relative changes observed for the two binary [(mPEG2)2Im]I-Ar and [C8C1Im][PF6]-Ar subsystems, respectively. For the surface tension, the absolute changes at a given pressure are very similar regardless of the IL bulk composition, suggesting a similar weak Ar enrichment at the gas–liquid interface.

Surface Affinity of Tetramethylammonium Iodide in Aqueous Solutions: A Combined Experimental and Computer Simulation Study.

The surface affinity of tetramethylammonium iodide (TMAI) in aqueous solutions is investigated by surface tension measurements and molecular dynamics computer simulations. Experiments, performed in the entire composition range of solubility using the pendant drop method with two different setups, clearly reveal that TMAI is a weakly capillary active salt. Computer simulations performed with the AMBER force field reproduce the experimental data very well, while two other major force fields (i.e., CHARMM and OPLS) can still reproduce the experimental trend qualitatively; however, even qualitative reproduction of the experimental trend requires scaling down the ion charges according to the Leontyev-Stuchebrukhov correction. On the other hand, the GROMOS force field fails in reproducing the experimentally confirmed capillary activity of TMAI. Molecular dynamics simulation results show that, among the two ions, iodide has a clearly larger surface affinity than tetramethylammonium (TMA+). Further, the adsorption of the I- anions is strictly limited to the first molecular layer beneath the liquid-vapor interface, which is followed by several layers of their depletion. On the other hand, the net negative charge of the surface layer, caused by the excess amount of I- with respect to TMA+, is compensated by a diffuse layer of adsorbed TMA+ cations, extending to or beyond the fourth molecular layer beneath the liquid surface.

The effect of SiO2 nanoparticles and surfactant on the wetting properties of an enzyme-based nanofluid as a liquid binder in the enzyme granulation process

This study investigated the effect of SiO2 nanoparticles and SDS surfactant on the wetting properties of an enzyme-based liquid binder and granule size distribution in a fluidized bed granulation process. The nanofluids were prepared by adding different SiO2 and SDS concentrations to the alkaline protease enzyme liquor with sodium carboxymethylcellulose as the granulating binder. The surface tension (ST) and contact angle (CA) of nanofluids with powder compact were measured by the pendant and sessile drop methods. A new correlation was also proposed for the ST of nanofluids. Furthermore, the influence of the nanoparticle and surfactant on the enzyme activity of nanofluids was evaluated. The results showed that nanoparticles increased both ST and CA of the base fluid, while the SDS had the opposite effect. The granulation results revealed the granule size was increased by increasing the adhesion tension of the binder, whereas the size distribution became narrower and more uniform.

Experimental and modelling study of the interfacial tension of (n-decane + carbon dioxide + water) in the three phase region

The interfacial tensions (IFTs) between hydrocarbon-, water- and CO2-rich phases are important in the processes of carbonated water injection for enhanced oil recovery and carbon geological storage. In this work, the IFTs between decane-rich and water-rich phases, in the presence of the third CO2-rich phase, were measured by the pendant drop method and modelled with the density gradient theory at temperatures from 298.15 K to 353.15 K and at pressures up to the critical point pressure of (CO2 + decane) (maximum 11 MPa at 353 K). The dynamic IFT decreased over time due to CO2 adsorption on the interface and mass transfer into the decane-rich drop until equilibrium was reached. As expected, the equilibrium IFTs were observed to decrease with increasing pressure. At low pressures, the equilibrium IFTs decreased with increasing temperature while, at high pressures, the reverse was observed. By comparing the IFTs of ternary (decane + CO2 + H2O) system with those of binary (decane + H2O) system, it was found that CO2 could reduce system IFT, for example by 15.2 mN/m at T = 333 K and p = 10 MPa. The extent of reduction depends on the solubility of CO2 in the liquid phases and the adsorption amount at the interface. Furthermore, the equilibrium IFT was found to be linearly dependent on the CO2 concentration in the water-rich phase isothermally, and an empirical relation was developed with an average absolute deviation of 0.3 mN/m. Density gradient theory coupled with the volume translated CPA equation of state was found to provide an accurate description of the IFTs with an average absolute deviation of 0.8 mN/m, proving its capability of predicting IFTs of (alkane + CO2 + water) in the three-phase region. The density profile in the interfacial region is also demonstrated. There is an enrichment of CO2 molecules at the interface and the enrichment is more pronounced with increasing pressure or decreasing temperature.

Determination of Density and Surface Tension of CaO–SiO2–Al2O3 Molten Slag by Pendant Drop Method

Determination of Density and Surface Tension of CaO–SiO2–Al2O3 Molten Slag by Pendant Drop Method

Formation Damage Caused by Wax Deposition Results in Shale Production Decline

_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 210414, “First Evidence for Shale Production Decline as a Result of Formation Damage Caused by C60+ Paraffin Wax Deposition: A Permian Case Study,” by Amir Mahmoudkhani, SPE, Locus Fermentation Solutions, and Jonathan Rogers and Martin Shumway, SPE, Locus Bio-Energy Solutions, et al. The paper has not been peer reviewed. _ Analysis of production decline curves revealed that three candidate wells in West Texas depleted faster than indicated by a type decline curve, indicating a potentially abnormal permeability-reduction mechanism. A biosurfactant-based squeeze program was recommended and applied in three horizontal wells. The biosurfactant treatment offers an alternative and economical method for remediation of formation damage caused by high‑molecular‑weight paraffin wax deposition in porous media that does not require costly intervention techniques to apply. Introduction The Bone Springs horizontal oil play in the Delaware Basin spans from southeast New Mexico into West Texas. Stacked, multipay reservoirs, each with diverse rock properties, possess upside but also complexity. The initial targets in the play were conventional sandstones. Wells then tapped into carbonate lenses and, ultimately, low-permeability sandstones. As a result of horizontal drilling technology combined with hydraulic fracturing, very thin sands and other facies are now being produced. Generally, reservoir quality of this unconventional hydrocarbon system is controlled by carbonate content, where increased carbonate content typically is associated with lower productivity. Experimental Methods All crude oils exhibited precipitation of organics at ambient laboratory temperatures. Even after storing crudes at the bottomhole temperature of 140°F, a small amount of wax remained insoluble in bulk liquid. Samples of formation drill cuttings were received for various depth intervals between 8,500 and 12,000 ft. X‑ray diffraction analyses of solids revealed quartz as the major mineral phase, with clays and carbonates account for remaining phases. Combined fractions with 160-micron size were used for microcolumn oil-recovery screening tests. Carbon distributions of oils and waxes were performed by high-temperature gas chromatography (HTGC). The Du Noüy ring method was used to measure static surface tensions of biosurfactant solutions at different concentrations and was applied to calculate critical micelle concentrations at ambient temperature. Interfacial tension (IFT) measurements were performed using a drop-shaped tensiometer using the pendant-drop method. Finally, the IFTs of oil in synthetic formation water and in biosurfactant solutions prepared in city tap water were determined. Contact-angle measurements also were performed. The wax-appearance temperature (WAT) of crude and wax samples was determined by the differential scanning calorimetry method. Spontaneous imbibition experiments were performed using the Amott-cell method at reservoir temperature. Berea sandstone core plugs (25×50 mm) with a permeability of 385 md and porosity of 18.4% were used. Core plugs were saturated with homogenized crude oil samples at 140°F for 7 days.

Interfacial tension of water near to critical conditions by using the pendant drop method: New experimental data and a correlation based on the parachor method

The interfacial tension (IFT) at vapor/liquid equilibrium was measured for the pure water system following the saturation line (further named as water (l)/water (v) or pure water) as well as for the binary water/nitrogen system (further named water/nitrogen). In order to obtain vapor/liquid IFT data, the pendant drop method was applied in a high-pressure-high temperature view cell. The vapor/liquid IFT of the binary water/nitrogen system was investigated at 10, 15 and 18 MPa and for temperatures in the range of 323–598 K. For the water (l)/water (v) system, the temperature ranges from 423 K to 623 K at the respective saturation pressure. The IFT of the binary water/nitrogen system is in a similar range compared to the IFT of the pure water system up to temperatures of 500 K although showing an influence of the nitrogen pressure due to solubility and adsorption effects. At temperatures above 500 K, the IFT starts to considerably differ as a function of temperature, reflecting the respective phase behaviour of both systems. The parachor method following Macleod-Sugden was used to correlate the IFT of the binary water/nitrogen system, as well as the pure water system. The equation is in good agreement with the experimental results, showing an AAD of 4.97% for the water/nitrogen system and 3.02% for the pure water system. The obtained experimental results are further in good agreement with comparable literature data.

Influence of dissolved argon or carbon dioxide on the viscosity and surface tension of the imidazolium-based ionic liquids [OMIM][PF6] or [m(PEG2)2IM

The present study investigates the influence of dissolved gases on the viscosity and surface tension of ILs at saturation conditions. As model systems, the imidazolium-based ILs, namely, the hydrophobic 1-methyl-3-octylimidazolium hexafluorophosphate ([OMIM][PF6]) and the hydrophilic 1,3-bis(2-(2-methoxyethoxy)ethyl)imidazolium iodide ([(mPEG2)2IM]I), were studied in combination with argon (Ar) and carbon dioxide (CO2) representing gases of relatively low and high solubility. By a combination of surface light scattering (SLS) and the pendant-drop (PD) method within one setup and sample cell, the surface tension determined by the PD method was used to access the saturated viscosity of the liquid bulk phase via SLS at temperatures of (303 and 323) K and pressures from (0.02 up to 8) MPa. At the same states and within the same setup, the gas solubility in the ILs was estimated on the basis of the evolution of the pressure during transient gas absorption. The addition of either gas causes a decrease in the surface tension of both ILs, which is more pronounced for CO2 at a given pressure and for the lower temperature. This behavior seems to be related to the weakening of intermolecular interactions at the gas–liquid interface by adding gas, facilitated by possible surface enrichment effects of CO2. The viscosity of both ILs is distinctly lowered with increasing CO2 pressure, amounting to a factor of 14 for [OMIM][PF6] at the largest pressure of 5 MPa. In the presence of Ar, the viscosity of [OMIM][PF6] reduces with increasing pressure by 11% at 8 MPa, while that of [(mPEG2)2IM]I increases by 7%. This behavior indicates that the fluidization effect on the liquid phase due to the solvation of Ar is dominant for the hydrophobic IL with higher Ar solubility, whereas it is outweighed by the competing compression effect of the gas for the hydrophobic IL.

Interfacial rheology for probing the in-situ chemical reaction at interfaces of molten polymer systems

The design of new functional materials from immiscible polymers or multi-layered structures using reactive compatibilisation is an efficient approach that has been extensively employed in a wide range of applications. The adhesion/interfacial properties in these multiphase polymeric systems depend on the extent of reaction occurring at the interface. However, probing in-situ interfacial reactions in the molten state has proved challenging. In this study, interfacial shear rheology is used for the first time to directly probe the reaction at the interface between maleic anhydride-grafted polyethylene (PEgMA) and aminopropyl-terminated polydimethylsiloxane (PDMS-(PropNH2)2) used as model reactive polymer systems. Then the reaction at the interface was investigated using interfacial shear rheology based on a newly homemade, lightweight biconical setup. Thereafter, the time evolution of the interfacial tension with the progress of interfacial reaction was assessed using the pendant drop method. First, the extent of reaction was checked using differential scanning calorimetry (DSC) and dynamic rheology coupled with fast-scan FTIR spectroscopy. It has been demonstrated that the molecular weight of the aminated PDMS and the temperature of the medium markedly affect the rate of melt reaction at the interface and related interfacial rheological properties. Interestingly, the ability to assess the reactions at the interface in PEgMA/PDMS-(PropNH2)2 systems, even with low concentrations of reactive functionalities, demonstrates that interfacial rheology is a suitable, sensitive probe that could be applied to other reactive polymer systems, allowing better control of the resulting physical properties.

Effect of cationic and anionic surfactants on the wettability and interfacial tension of oil-brine systems in analogous rocks from the Chicontepec Paleochannel, Mexico

The chemical enhanced oil recovery (cEOR) uses substances to improve the mobility of petroleum in reservoirs. Among these substances are the surfactants, whose purpose is to change the wettability and interfacial tension (IFT). We focus on experiments of surfactants in rocks from Chicontepec Paleochannel. CTAB, DTAB and SDS surfactants in brines of NaCl and KCl and mineral oil were investigated for reduction of IFT and contact angle alteration. The sessile and pendant drop methods were used to determine the IFT. The electrical affinity of the rock surface, dissolved ions, and the surfactant molecules, play key roles in the alteration of wettability and IFT. Thus, one scheme of interactions between the electrical charges is proposed on the basis of the rocky characterization and the following results: the lowest contact angle was 106° with CTAB at 0.01 wt% in brines at 9.25 g/L NaCl, and 108° with SDS at 0.01 wt% in brines at 20 g/L NaCl. The smallest IFT was 0.813 dyn/cm with CTAB at 0.5 wt% in brines at 5 g/L KCl. This work serves as first assessments of these surfactants to enhance the production in Chicontepec, employing cheap tensoactives to increase the applicability. Besides, these results will guide future displacement tests as cEOR lab simulation.

Anionic amphiphilic copolymers as potential agents for enhanced oil recovery

To develop “smart fluids” for enhanced oil recovery from reservoir rocks, comb-type amphiphilic copolymers were synthesized through free radical polymerization (FRP) of: (i) the hydrophilic, anionic monomer 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPSA) that offer a hydrophilic character to the final copolymers; (ii) the weakly acidic hydrophilic monomer acrylic acid (AA); (iii) the hydrophobic monomer dodecyl methacrylate (DMA). The polymers were characterized by Proton Nuclear Magnetic Resonance (1H NMR), Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR), fluorescence probing, Dynamic Light Scattering (DLS) and electrophoresis. Stable polymer solutions were prepared without and with the presence of salts (NaCl, CaCl2, MgSO4). The dynamic air/water surface and oil/water interfacial tensions were measured by the pendant drop method, and their steady-state values were estimated with fitting to asymptotic relations predicting the long-time behavior. Moreover, the wettability of water/air and water/oil to glass or poly(methyl methacrylate) (PMMA) surface was quantified by measuring the contact angles. Oil-in-water Pickering emulsions were prepared by mixing n-dodecane with polymer solutions and their stability was evaluated macroscopically with optical inspection, and microscopically by measuring the oil drop size distribution and shear viscosity. Polymer solutions and Pickering emulsions were tested as agents for the displacement of the residual n-dodecane from a glass-etched pore network. The long-lasting retention of polymer solution in the pore network makes the solid surface more hydrophilic, facilitating the fission of oil ganglia into smaller ones which are mobilized easier, resulting in a final EOR efficiency between 10% and 18%. When using an emulsion as displacing fluid, the viscosity ratio and capillary number increase by orders of magnitude, the viscous forces prevail against the capillary ones, and the growth pattern becomes a frontal drive leading to a high EOR efficiency of ∼94%.

Rosensweig Instability Study of Iron Oxide Nano Fluid Under Uniform Magnetic Field

We report the synthesis of magnetic nanofluids and the investigations on the formation of surface instabilities of ferrofluid when exposed to a normal uniform magnetic field. Ferrofluid of iron oxide particles with an average size of 9 nm, dispersed in a kerosene base is synthesized by a well-known chemical method. The structural analysis of the nanoparticles is carried out by employing X-ray diffraction technique. Fourier Transform Infrared Spectroscopy studies revealed the chemical binding with the surfactant. The Dynamic Light Scattering studies are performed to determine the hydrodynamic size of the suspended particles. The constancy in hydrodynamic size obtained for different particle concentrations is indicative of agglomeration-free suspension. The magnetic properties have been analyzed by the Superconducting Quantum Interference Device. The magnetization measurement signifies the superparamagnetic nature of particles. The temperature-dependent relaxation studies were carried out by field cooled (FC) and zero field cooled (ZFC) moment measurements at a constant applied field. We have demonstrated the Rosensweig instability experimentally and observed the pattern transition. The surface takes on a hexagonal pattern when the applied field surpasses the critical field, which shifts to a square pattern when the applied field reaches a second threshold. The surface tension of the fluid is measured by the pendant drop method and is correlated with the results obtained through instability measurement. The magnetic concentration of the sample is determined from the Thermo gravimetric analysis.

Interfacial tensions of (brine + H2 + CO2) systems at gas geo-storage conditions

In hydrogen geological storage, cushion gas has vital role to retain adequate reservoir pressure to keep the hydrogen withdrawal stable. Presence of the cushion gas in the storage reservoir can affect the flow characteristics of hydrogen during injection and production cycles. One of the most crucial parameters that control the fluids flow in porous media is interfacial tension (IFT) between fluids. However, the literature data lacks in terms of IFT between cushion gas mixed with hydrogen and brine at geo-storage conditions. In this study, the pendant drop method was used to measure the IFT of (brine + H2 + CO2) system at different CO2 fractions as cushion gas, reservoir temperature, reservoir pressure, and water salinity. The results showed that the IFT reduced with increasing CO2 percentage. Moreover, IFT declined when pressure went up gradually. This pattern was almost linear at lower proportion of CO2; however, a non-linear trend was observed at higher percentage of CO2. In addition, at constant pressure, IFT decreased with temperature. These results also demonstrated that the IFT increases linearly with brine salinity. This work thus presents new dataset for hydrogen geological storage projects, where large-scale hydrogen with CO2 (as a cushion gas) can be stored in geological formations.